Shoulder joint replacement surgery (also called shoulder arthroplasty) can effectively ease pain from shoulder arthritis. Most people experience improved shoulder function after this surgery. But, certain patients are not candidates for joint replacement of the shoulder because they lack the muscle function necessary to stabilize the joint. A different type of shoulder replacement, called reverse shoulder replacement, may be available for many of these patients and provide pain relief as well as a stable functioning shoulder.
A conventional shoulder replacement device mimics the normal anatomy of the shoulder: a plastic "cup" is fitted into the shoulder socket (glenoid), and a metal "ball" is attached to the top of the upper arm bone (humerus). In a reverse total shoulder replacement, the socket and metal ball are switched. The metal ball is fixed to the socket and the plastic cup is fixed to the upper end of the humerus.
In a healthy shoulder, the "ball" of the humerus is held in the shoulder socket by several muscles and tendons, including the rotator cuff tendon.
A reverse total shoulder replacement works better for people with cuff tear arthropathy because it relies on different muscles to move the arm. In a healthy shoulder, the rotator cuff muscles help position and power the arm during range of motion. A conventional replacement device also uses the rotator cuff muscles to function properly. In a patient with a large rotator cuff tear and cuff tear arthropathy, these muscles no longer function. The reverse total shoulder replacement relies on the deltoid muscle, instead of the rotator cuff, to power and position the arm.
What parts of the shoulder are involved?
The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone), and the clavicle (collarbone).
The rotator cuff connects the humerus to the scapula. The rotator cuff is formed by the tendons of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis.
Muscles move bones by pulling on the tendons. The rotator cuff helps raise and rotate the arm. As the arm is raised, the rotator cuff also keeps the humerus tightly in the socket. A part of the scapula, called the glenoid, makes up the socket of the shoulder. The glenoid is very shallow and flat.
The part of the scapula that connects to the shoulder is called the acromion. A bursa is located between the acromion and the rotator cuff tendons. A bursa is a lubricated sac of tissue that cuts down on the friction between two moving parts. Bursae are located all over the body where tissues must rub against each other. In this case, the bursa protects the acromion and the rotator cuff from grinding against each other.
The humeral head of the shoulder is the ball portion of the joint. The humeral head has several blood vessels, which enter at the base of the articular cartilage. Articular cartilage is the smooth, white material that covers the ends of bones in most joints. Articular cartilage provides a slick, rubbery surface that allows the bones to glide over each other as they move. Cartilage also functions as sort of a shock absorber.
The shoulder joint is surrounded by a watertight sac called the joint capsule. The joint capsule holds fluids that lubricate the joint. The walls of the joint capsule are made up of ligaments. Ligaments are connective tissues that attach bones to bones. The joint capsule has a considerable amount of slack, loose tissue, so that the shoulder is unrestricted as it moves through its large range of motion.
This procedure to replace your shoulder joint with an artificial device.
Your surgeon will make an incision either on the front or the top of your shoulder. He or she will remove the damaged bone and then position the new components to restore function to your shoulder.
The components of a reverse total shoulder replacement include the metal ball that is screwed into the shoulder socket, and the plastic cup that is secured into the upper arm bone.
The reverse shoulder replacement surgery is performed almost identically to the normal shoulder replacement - except different artificial parts are inserted.
You will most likely need general anesthesia for shoulder replacement surgery. General anesthesia puts you to sleep. It is difficult to numb only the shoulder and arm in a way that makes such a major surgery possible. While nerve blocks can be helpful with postoperative pain control, they are not usually effective enough to be used as the only anesthetic for this kind of operation.
Shoulder replacement surgery is done through an incision on the front of your shoulder. This is called an anterior (deltopectoral) approach. For reverse shoulder replacements, especially for patients with multiple previous surgeries, a superior approach through the deltoid muscle may be used. The surgeon cuts through the skin and then isolates the nerves and blood vessels and moves them to the side. The muscles are also moved to the side.
The surgeon enters the shoulder joint itself by cutting into the joint capsule. This allows the surgeon to see the joint. In more advanced cases of cuff tear arthropathy, and in patients with previous surgery, there may be no capsule and rotator cuff remaining.
At this point, the surgeon can prepare the bone for attaching the replacement parts. The ball portion of the humeral head is removed with a bone saw. The hollow inside of the upper humerus is prepared using a rasp. This lets your surgeon mold the space to anchor the metal stem of the humeral component inside the bone.
After surgery, you will feel some pain. This is a natural part of the healing process. Your doctor and nurses will work to reduce your pain, which can help you recover from surgery faster.
Medications are often prescribed for short-term pain relief after surgery. Many types of medicines are available to help manage pain, including opioids, nonsteroidal anti-inflammatory drugs (NSAIDs), and local anesthetics. Your doctor may use a combination of these medications to improve pain relief, as well as minimize the need for opioids.
When you leave the hospital, your arm will be in a sling. Your surgeon may instruct you to do gentle range of motion exercises to increase your mobility and endurance. A formal physical therapy program may also be recommended to strengthen your shoulder and improve flexibility.
You should be able to eat, dress, and groom yourself within a few weeks after surgery.
Your surgeon may ask you to return for office visits and x-rays in order to monitor your shoulder.
After rehabilitation, you will most likely be able to lift your arm to just above shoulder height and bend your elbow to reach the top of your head or into a cupboard. Reverse total shoulder replacement provides outstanding pain relief and patient satisfaction is typically very high.